Ejector/Mixer Nozzle for Noise Reduction

ABSTRACT

An inlet bleed heat system in a gas turbine includes a compressor discharge extraction manifold that extracts compressor discharge air, an inlet bleed heat manifold receiving the compressor discharge air, and a plurality of acoustic dispersion nozzles disposed at an output end of the inlet bleed heat manifold that reduce a velocity of the compressor discharge air in the inlet bleed heat manifold. Noise is generated from the shearing action between the surrounding atmosphere and air jets from orifices. When the air jet velocity is slowed using, for example, a multi-stage ejector/mixer, noise can be abated.

BACKGROUND OF THE INVENTION

The invention relates to noise reduction in a gas turbine and, moreparticularly, to the use of a multiple stage ejector/mixer nozzle in agas turbine inlet bleed heat application to reduce noise.

The combustion system of a gas turbine generates hot gases to drive aturbine. The turbine, in turn, drives a compressor that providescompressed air for combustion in the combustion system. The turbineproduces usable output power.

In some gas turbine applications, there are instances of gas turbineplant operation where the gas turbine pressure ratio reaches theoperating pressure ratio limit of the compressor, resulting incompressor surge. These instances may arise in applications where lowBTU fuels or any other fuels with large amounts of diluent injection areused and/or at cold ambient temperature conditions. The compressorpressure ratio is typically larger than the turbine pressure ratio inthat the latter is subject to pressure loss in the turbine combustor.

One common solution that has been used to provide compressor pressureratio protection is the bleeding off of gas turbine compressor dischargeair and recirculating the bleed air back to the compressor inlet. Thismethod of gas turbine operation, known as Inlet Bleed Heat (IBH)Control, raises the inlet temperature of the compressor inlet air bymixing the colder ambient air with the bleed portion of the hotcompressor discharge air, thereby reducing the air density and the massflow to the gas turbine.

When a gas turbine bleeds compressor air into the inlet duct, it createsnoise that can exceed noise limits. Existing designs place the bleedingmanifolds downstream of inlet silencing panels. This arrangement canaddress an icing problem of the compressor IGV, but does notsufficiently solve the problem of inlet filter housing icing. If thebleeding manifolds are placed before the silencers in the inlet duct toaddress the icing problem, the noise problem arises.

A silencing nozzle was proposed for an IBH system. Silencing nozzles,however, are expensive. A related problem has been addressed in aircraftengine technology, using an ejector/mixer nozzle to reduce aircraftengine noise. The noise results from shearing action between thesurrounding atmosphere and air jets from orifices. After a multi-stageejector/mixer, the jet velocity is slowed down significantly, therebyreducing noise. There is currently no similar technology to reduce noisein a gas turbine.

It would thus be desirable for an IBH system to include an ejector/mixernoise reduction nozzle to enhance the mixing of hot air in the turbinewithout the use of expensive components.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment, an inlet bleed heat system in a gas turbineincludes a compressor discharge extraction manifold that extractscompressor discharge air, an inlet bleed heat manifold receiving thecompressor discharge air, an inlet filter housing disposed upstream ofthe inlet bleed heat manifold, and an inlet silencer disposed downstreamof the inlet bleed heat manifold. A plurality of acoustic dispersionnozzles are disposed at an output end of the inlet bleed heat manifoldand between the inlet filter housing and the inlet silencer. Theacoustic dispersion nozzles serve to reduce a velocity of the compressordischarge air in the inlet bleed heat manifold by mixing the compressordischarge air with outside air from the inlet filter housing.

In another exemplary embodiment, an inlet bleed heat system in a gasturbine includes a compressor discharge extraction manifold thatextracts compressor discharge air, an inlet bleed heat manifoldreceiving the compressor discharge air, and a plurality of acousticdispersion nozzles disposed at an output end of the inlet bleed heatmanifold that reduce a velocity of the compressor discharge air in theinlet bleed heat manifold.

In yet another exemplary embodiment, a method for reducing noise in aninlet bleed heat system of a gas turbine includes the steps ofextracting compressor discharge air; directing the compressor dischargeair into an inlet bleed heat manifold; and reducing a velocity of thecompressor discharge air in the inlet bleed heat manifold by mixing thecompressor discharge air with outside air via an inlet filter housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a gas turbine including an inletbleed heat system;

FIG. 2 is a perspective view showing a position of ejector/mixer nozzlesbetween the inlet filter and an inlet silencer;

FIG. 3 is a close-up view of the inlet bleed heat manifold shown in FIG.2; and

FIG. 4 is a detailed view of one branch from the inlet bleed heatmanifold including an exemplary nozzle.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an inlet bleed heat system 10 is schematicallyillustrated. Inlet bleed heat (IBH) is typically used to protect the gasturbine compressor from icing when operating at reduced IGV angles.Moreover, IBH systems are used to reduce compressor pressure ratio atcertain operating conditions where additional compressor operatingmargin is required. As illustrated, a compressor discharge extractionmanifold 12 is provided for extracting compressor discharge air, whichflows through a manual isolation valve 14 and a control valve 16 to aninlet bleed heat manifold 18 disposed downstream of an inlet air filterhousing 20 and an inlet silencer 22. In the illustrated system, a drainvalve 24 is provided for diverting condensate.

An output end of the inlet bleed heat manifold 18 includes a pluralityof acoustic dispersion nozzles 26. The nozzles 26 serve to reduce avelocity of the compressor discharge air in the inlet bleed heatmanifold 18 by mixing the compressor discharge air with outside air fromthe inlet filter housing 20. FIG. 2 shows the output end of the inletbleed heat manifold 18 positioned between the inlet filter housing 20and the inlet silencer 22. With reference to FIGS. 2 and 3, the inletbleed heat manifold 18 includes a main manifold 28 and a plurality ofbranch manifolds 30 connected to the main manifold 28. The acousticdispersion nozzles 26 are disposed on the branch manifolds 30. FIG. 4 isa close-up view of a branch manifold 30 and an exemplary nozzle 26.Those of ordinary skill in the art will appreciate alternative suitabledesigns for the nozzle 26, and the invention is not meant to be limitedto the exemplary nozzle illustrated in FIG. 4.

The described system incorporates an ejector/mixer noise reductionnozzle to enhance the mixing of hot air in the turbine without the useof expensive components. By mixing the compressor discharge air withoutside air from the inlet filter housing in the ejector/mixer nozzles,a velocity of the compressor discharge air in the inlet bleed heatmanifold can be reduced, thereby reducing noise.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. An inlet bleed heat system in a gas turbine comprising: a compressordischarge extraction manifold that extracts compressor discharge air; aninlet bleed heat manifold receiving the compressor discharge air; aninlet filter housing disposed upstream of the inlet bleed heat manifold;an inlet silencer disposed downstream of the inlet bleed heat manifold;and a plurality of acoustic dispersion nozzles disposed at an output endof the inlet bleed heat manifold and between the inlet filter housingand the inlet silencer, the acoustic dispersion nozzles reducing avelocity of the compressor discharge air in the inlet bleed heatmanifold by mixing the compressor discharge air with outside air fromthe inlet filter housing.
 2. An inlet bleed heat system according toclaim 1, wherein the plurality of acoustic dispersion nozzles compriseejector/mixer noise reduction nozzles.
 3. An inlet bleed heat systemaccording to claim 1, wherein the inlet bleed heat manifold comprises amain manifold and a plurality of branch manifolds connected to the mainmanifold, and wherein the plurality of acoustic dispersion nozzles aredisposed on the branch manifolds.
 4. An inlet bleed heat system in a gasturbine comprising: a compressor discharge extraction manifold thatextracts compressor discharge air; an inlet bleed heat manifoldreceiving the compressor discharge air; and a plurality of acousticdispersion nozzles disposed at an output end of the inlet bleed heatmanifold, the plurality of acoustic dispersion nozzles reducing avelocity of the compressor discharge air in the inlet bleed heatmanifold.
 5. An inlet bleed heat system according to claim 4, whereinthe plurality of acoustic dispersion nozzles comprise ejector/mixernoise reduction nozzles.
 6. An inlet bleed heat system according toclaim 4, wherein the inlet bleed heat manifold comprises a main manifoldand a plurality of branch manifolds connected to the main manifold, andwherein the plurality of acoustic dispersion nozzles are disposed on thebranch manifolds.
 7. A method for reducing noise in an inlet bleed heatsystem of a gas turbine, the method comprising: extracting compressordischarge air; directing the compressor discharge air into an inletbleed heat manifold; and reducing a velocity of the compressor dischargeair in the inlet bleed heat manifold by mixing the compressor dischargeair with outside air via an inlet filter housing.
 8. A method accordingto claim 7, wherein the reducing step comprises exhausting the inletbleed heat manifold through a plurality of acoustic dispersion nozzlesdisposed at an output end of the inlet bleed heat manifold and betweenthe inlet filter housing and an inlet silencer.
 9. A method according toclaim 7, wherein the inlet bleed heat manifold comprises a main manifoldand a plurality of branch manifolds connected to the main manifold, andwherein the method comprises disposing the acoustic dispersion nozzleson the branch manifolds.